1. Field of the Invention
The present invention relates to a heat sink and a heat sink fan.
2. Description of the Related Art
Conventionally, a heat sink fan is utilized as a cooling device which cools a CPU mounted in a computer. The heat sink fan is a combination of a heat sink of metal to which the heat from the CPU is transmitted with a fan. The heat sink includes a plurality of fins arranged in a circumferential direction. The heat transmitted from the CPU to the heat sink is efficiently radiated by the air sent by the fan to the heat sink.
Japanese Laid-Open Patent Publication No. 2009-206404 and Japanese Laid-Open Patent Publication No. 2004-336031 disclose a radiating fin which branches into two portions on a radially outer side. Japanese Laid-Open Patent Publication No. 2008-91644 discloses a radiating fin which branches into three branch fins on the radially outer side.
In a heat sink in which each radiating fin branches into two branch fins on the radially outer side, the branch points of all of the fins are arranged on the inner side, so as to increase the surface area. This arrangement may increase the radiating efficiency of the heat sink. However, in such a heat sink, a width of a gap between branch fins in the radiating fin or a width of a gap between fins is narrow. If the width of respective gap is excessively narrow, the flow of air from the fan is blocked. Thus, it is impossible to increase the radiating efficiency of the heat sink.